pgsql: Make some functions immutable.

Log Message:
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Make some functions immutable.

thanks Marko Kreen

Modified Files:
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pgsql/contrib/uuid-ossp:
uuid-ossp.sql.in (r1.1 -> r1.2)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/uuid-ossp/uuid-ossp.sql.in.diff?r1=1.1&r2=1.2)